Modern mountain biking was born on the trails of Mount Tamalpais in Marin County in the 1970s. We talk to some of the pioneers of the sport who are featured in a new documentary, "Klunkerz."Host: Scott ShaferGuests:• Charlie Kelly, creator of the Repack races and founder of the first magazine devoted to mountain biking• Gary Fisher, founder of Gary Fisher Bicycles and mountain biking icon.• Joe Breeze, founder of Breezer Bikes• Wende Cragg, one of the first female mountain bikers and a photographer whose pictures are featured in "Klunkerz."